This invention relates a multiservice advanced antenna, formed by a set of polygonal elements, supported by a transparent conductive layer coated on the transparent window of a motor vehicle.
The particular shape and design of the polygonal elements, preferably triangular or square, enhances the behavior of the antenna to operate simultaneously at several bands.
The multiservice antenna will be connected to most of the principal equipments presents in a motor vehicle such as radio (AM/FM), Digital Audio and Video Broadcasting (DAB and DVB), Tire pressure control, Wireless car aperture, Terrestrial Trunked Radio (TETRA), mobile telephony (GSM 900-GSM 1800-UMTS), Global Positioning System (GPS), Bluetooth and wireless LAN Access.
Until recently, telecommunication systems present in an automobile were limited to a few systems, mainly the analogical radio reception (AM/FM bands). The most common solution for these systems is the typical whip antenna mounted on the car roof. The current tendency in the automotive sector is to reduce the aesthetic and aerodynamic impact due to these antennas by embedding them in the vehicle structure. Also, a major integration of the several telecommunication services into a single antenna would help to reduce the manufacturing costs or the damages due to vandalism and car wash equipments.
The antenna integration is becoming more and more necessary as we are assisting to a profound change in telecommunications habits. The internet has evoked an information age in which people around the globe expect, demand, and receive information. Car drivers expect to be able to drive safely while handling e-mail an telephone calls and obtaining directions, schedules, and other information accessible on the WWW.
Telematic devices can be used to automatically notify authorities of an accident and guide rescuers to the car, track stolen vehicles, provide navigation assistance to drivers, call emergency roadside assistance and remote diagnostics of engine functions.
High equipments and services have been available on some cars for very few years. High equipment and service costs initially limited them to luxury cars. However, rapid declines in both equipment and service prices are bringing telematic products into mid-priced automobiles. The massive introduction of new systems will generate a proliferation of new car antennas, in contradiction with the aesthetic and aerodynamic requirements of integrated antennas.
Antennas are essentially narrowband devices. Their behavior is highly dependent on the antenna size to the operating wavelength ratio. The use of fractal-shaped multiband antennas was first proposed in 1995 (U.S. Pat. No. 9,501,019). The main advantages addressed by these antennas were a multifrequency behavior, that is the antennas featured similar parameters (input impedance, radiation pattern) at several bands maintaining their performance, compared with conventional antennas. Also, fractal-shapes permit to obtain antenna of reduced dimensions compared to other conventional antenna designs, as well.
In 1999, multilevel antennas (PCT/ES/00296) resolved some practical problems encountered with the practical applications of fractal antennas. Fractal auto-similar objects are, in a strict mathematic sense, composed by an infinite number of scaled iterations, impossible to achieve in practice. Also, for practical applications, the scale factor between each iteration, and the spacing between the bands do not have to correspond to the same number. Multilevel antennas introduced a higher flexibility to design multiservice antennas for real applications, extending the theoretical capabilities of ideal fractal antennas to practical, commercial antennas
Several solutions were proposed to integrate the AM/FM antenna in the vehicle structure. A possible configuration is to use the thermal grid of the rear windshield (Patent No WO95/11530). However, this configuration requires an expensive electronic adaptation network, including RF amplifiers and filters to discriminate the radio signals from the DC source. Moreover, to reduce costs, the AM band antenna often comes apart from the heating grid limiting the area of the heating grid.
Other configuration is based on the utilization of a transparent conductive layer. This layer is coated on the vehicle windshield is introduced to avoid an excessive heating of the vehicle interior by reflecting IR radiations.
The utilization of this layer as reception antenna for AM or FM band has been already proposed with several antenna shapes. Japanese Patent JP-UM-49-1562 is often cited as one of the first to propose the utilization of transparent conductive layer as reception antenna. U.S. Pat. No. 445,884 proposed to use the entire windshield conductive layer as impedance matching for FM band substantially horizontal antenna element. Others configurations proposed to leave a slot aperture between the windshield screen border and the conductive transparent layer (U.S. Pat. No. 5,355,144) or to impress odd multiple half wavelengths monopoles onto the crystal (U.S. Pat. No. 5,255,002).
Obliviously all these antenna configurations can only operate at a determinate frequency band in reason of the frequency dependence of the antenna parameter and are not suitable for a multiservice operation. One of the main substantial innovations introduced by the present invention consists in using a single antenna element, maintaining the same behavior for several applications, and to keep the IR protection. The advantages reside in a full antenna integration with no aesthetic or aerodynamic impact, a full protection from vandalism, and a manufacturing cost reduction.
The present invention relates an antenna for a motor vehicle with the following parts and features
a) a transparent window coated with an optically transparent conducting layer on at least one side of any of the window material layers
b) a multilevel structure impressed on this conducting layer. This multilevel structure is composed by a set of polygonal elements of the same class, preferably triangles or squares.
c) a two-conductor feeding transmission line
d) a similar impedance at the feeding point and a similar horizontal radiation pattern in at least three frequencies within three bands, wherein two of said three frequencies are selected from the following: FM, DAB, Tire pressure control, Wireless car aperture, Tetra, DVB, GSM900/AMPS, GSM1800/DCS/PCS/DECT, UMTS, GPS, Bluetooth and WLAN.
The typical frequency bands of the different applications are the following:
FM (80 MHzxcx9c110 MHz)
DAB (205 MHzxcx9c230 MHz)
Tetra (350 MHzxcx9c450 MHz)
Wireless Car Aperture (433 MHz, 868 MHz)
Tire pressure Control (433 MHz)
DVB (470 MHzxcx9c862 MHz)
GSM900/AMPS (820 MHzxcx9c970 MHz)
GSM1800/DCS/PCS/DECT (1700 MHzxcx9c1950 MHz)
UMTS (1920 MHzxcx9c2200 MHz)
Bluetooth (2400 MHzxcx9c2500 MHz)
WLAN (4.5 GHzxcx9c6 GHz)
The main advantage of the invention is the multiband and multiservice behavior of the antenna. This permits a convenient and easy connection to a single antenna for the majority of communication systems of the vehicle.
This multiband behavior is obtained by a multilevel structure composed by a set of polygonal elements of the same class (the same number of sides), electromagnetically coupled either by means of an ohmic contact or a capacitive or inductive coupling mechanism. The structure can be composed by whatever class of polygonal elements. However, a preference is given to triangles or squares elements, being these structures more efficient to obtain a omnidirectional pattern in the horizontal plane. To assure an easy identification of each element composing the entire structure and the proper multiband behavior, the contact region between each of said elements has to be, in at least the 75% of the elements, always shorter than a 50% of the perimeters of said polygonal structures.
The other main advantage of the invention resides in the utilization of a transparent conductive layer as support for this antenna. Being transparent, this antenna can be coated in the windshield screen of a motor vehicle. Other possible positions are the side windows or the rear windows.
This optically transparent and conducting layer is habitually used in vehicle windshield screen to reflect the major part of IR radiations. The most common material used is ITO (indium tin oxide), although other materials may be used (like for instance TiO2, SnO or ZnO), by sputtering vacuum deposition process. An additional passive layer can be added to protect the said conducting layer from external aggression. Materials for this passivation layer are made, for instance, of SiO2, or any other material used for passivation obtained by vacuum deposition, or also a polymeric (resin) coating sprayed on the structure. During the sputtering process, a mask can be placed on the substrate material to obtain the desired multiband antenna shape. This mask normally is made of conducting special stainless steel or copper for this purposes, or a photosensitive conducting material to create the mask by photochemical processes This transparent conductive layer may be also connected to an heating source to defrost the window in presence of humidity or ice.
Other advantage of the multiband antenna is to reduce the total weight of the antenna comparing with classical whip. Together with the costs, the component weight reduction is one of the major priority in the automotive sector. The cost and weight reductions are also improved by the utilization of only single cable to feed the multiservice antenna.
This transparent conductive layer could be also deposited on support different than a transparent windshield or other vehicle windows. An adequate position could the vehicle roof to assure an optimum reception from satellite signals for instance.